Labyrinth stiffener



June 1, 1965 J. R. MONDT LABYRIN'IH STIFFENER Filed Dec. 18, 1962 IIUIIIIM [,9 TNVENTOR.

c/Gmes 7? 22201747 ATTORNEY United States Patent 3,186,479 LABYRINTH STIFFENER James R. Mondt, Warren, Mich., "assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Dec. 18, 1962, Ser. No. 245,577

SCIaims. (Cl. 165-10) different temperatures, the matrix carrying heat from the better to the coolerggas. In such devices, a seal is provided where the matrix passes from one space to the other through a diaphragm or bulkhead. Sealing is one of the 3,186,479 Patented June 1, 1965 ice.

Approximately one third of the matrix is to the left of the diaphragm, moving through a space which is divided by the matrix into a cool air zone 18 which may be supplied by the compressor of the gas turbine engine and a hot air zone 19 into which the air flows through the matrix. Combustion chambers (not illustrated) connected to the hot air zone 19 discharge through a turbine .(not illustrated) into a hot gas zone 23 within the matrix at the other side of the diaphragm, from which the exhaust gas flows through the matrix to space 25 from which it is discharged to the atmosphere.

- Referring now also to FIGURES 2 and 3 for the preferred structure, the matrix 9 is of an annular drum shape having .two rims 27, each of which may include a ring difficult problems in such regenerators, since there ordiis very slight, but slight clearances at the seals can cause very wasteful leakage. g

In response to this problem various eiforts have been made, with considerable success, to provide aseal which distorts along with the matrix. Another approach is to construct a matrixso that the thermal distortion is eliminated or minimized. My invention relates to a structure minimizing distortion of the matrix, and particularly of the portions of the matrix which cooperate with the dia-- phragm seals. While the invention is applicable to both axial-flow and radial-flow regenerators, its preferred em-- bodiment is in a radial-flow regenerator having two seals which surround the matrix at the two points where it passes through a diaphragm separating one gas space from the other, such as is described in United States patent applications Serial No. 559,390, filed January 16, 1956, (now Patent No. 3,057,604) and Serial No. 156,599, filed December 4, 1961. s 1

The principal object of the invention is to decrease the leakage of the seals of rotary regenerators and, therefore, improve the efliciency of power plants incorporating such regenerators. The nature of the invention and its advantages will be clearfrom the succeeding detailed description of the. preferred embodiment thereof, with reference to the accompanying drawings. 1

FIGURE 1 is a rather schematic cutaway view of a rotary regenerator embodying the invention, the view being taken on a plane perpendicular tothe axis of rotation.

FIGURE 2 is an enlarged partial view of the matrix taken in the same plane as FIGURE 1, with parts cut away. i

FIGURE 3 is a cross-section of the matrix taken on the plane indicated by the line 33 of FIGURE 2.

FIGURE 1 may be regarded as a simplified representation of the application of my invention to the regenerator of a gas turbine engine such as that described in US. patent application Serial No. 559,475, filed January 16, 1956 (now abandoned). In such an engine, a regenerator matrix 9 is suitably supported in a housing 10 for rotation about an axis A so that it passes twice through a bulkhead or diaphragm 11. Main seals 13 and 14 surround the matrix where it passes through the diaphragm. The means to support the matrix for rotation about the axis and to locate the seals 13and 14 are immaterial to this invention and will not be described.

or track 28 by which the matrix is supported and guided and a ring gear 29 by which it is driven. Stiifeners 31 of relatively heavy section are spaced'regularly around the periphery of the drum, extending from one rim to the other to couple the rims together rigidly. The stiffeners have lugs 33 extending from their ends received in circumferential grooves in the inner faces ofthe rims and held there by pins 34 which are inserted before the ring 28 is shrunk into place.

The spaces between the stiifeners .31 and extending from one rim to the other are filled with porous'heat transfer material which consists of two types of elements. The first of these are regularly spaced seal elements 36. Between each two seal elements there is a stack'or pack of heat transfer elements 37 which may be called a core. It will be noted that the seal elements 36 have opposite marginal portions which extend radially from the ele-. merits 37. The elements 37 may be regarded as the core of the matrix, and the elements 36 and 37 together constitute heat transfer material. These elements may be thin corrugated plates with the corrugations extending radially of the matrix so that small passages for air flow are defined between adjacent plates and heat is readily exchanged between the air or gas and the thin plates of the heat transfer material. If desired, alternative plates of the heat transfer material may be flat and corrugated; or other forms of heat exchange material, including those described in United States Patent No. 2,937,010, may be employed. In the preferred structure according to this invention the core elements 3'7 are corrugated sheets having the same end configuration as the stiffeners 31 so as to fit within the grooves in the rims. Each labyrinth element 36 comprises a plate or lamina 40, corrugated so that the corrugations extend radially of the matrix, and with tabs 41 extending from the ends of the lamina to enter the grooves in the rim. Each seal element 36 also includes two bars 42 and 43 which extend across the length of the lamina, preferably nearer the outer or cooler edge thereof, and which are spot-weldedor seam-welded to the lamina 40 so as to provide as nearly as possible a single rigid beam structure. It will be appreciated, of course, that the thin corrugated plate 40 has almost no stiffness. In other words, it can be deformed arcu- 'ately in its own plane by expanding the corrugations toward one edge and contracting the corrugations toward the other edge; With the bars 42 and 43 Welded to the peaks of each corrugation there is a relatively stiff structure involving the bars and the plate 40. If all these parts were of the same material, the temperature gradient in the direction from the upper edge to the lower edge in FIGURES 2 and 3 would operate to cause arcuate deformation of the bars and lamina. In other words, the hotter bar 43 would expand more than the cooler bar 42 and they would bow upwardly of the element as seen in FIGURE 3 and the very slight resistance of the corrugated sheet itself would make very little difference. In otherwords, the thermal expansion and the dimensions and spacing of the bars would determine the amount of will tend to bow them also.

. 3 I distortion of the seal element 36. According to my invention, by proper selection of materials for the bars 42 and 43, this distortion may be eliminated or minimized.

Control of the configuration of the seal element can be obtained by employing two bars 42 and43 which are of different coefficients of thermal expansion so that they expand the same amount linearly in response to the different temperatures to which they are subjected; (This is a correct statement subject to a qualification which will be mentioned.) With the two bars welded or brazed to the corrugations across the seal element 36 and at pre determined distances from the matrix axis, the bars remain straight and maintain the edges of the plate straight as well. If one bar expanded more than the other, there would, of course, be bowing, or a tendency to bow which could be counteracted by force.

It is clear. that, considering the seal elements 36 alone,

if selectionof the materials for bars 42 and 43 is such j that their'temperature co'eflicients of expansion are related to each other inversely as the temperature rises of the two bars,.ia structure which is invariant in contour with temperature is provided. It'merely expands as it becomes hotter. If the heat transfer material or core material 37 has no tendency to distort as, for example, if itis particulate matter, this is the end to the problem. However, if the core is made up of plates, even though they are very flexible dirnensioually such as the corrugated sheets T of shim material illustrated, these will have a tendency to bow and, by frictional interaction with the seal plates,

By increasing the difference between the expansion coeflicients of the bars 42. andf43 'so that. the seal plate 36 tends'to have a reversecurvature to' the normal, this factor due to loading by'thecore can also be compen- ,sa'ted for. An analysis of this factor is ditficult, if not; I

impossible, butthe correction cangbe made empirically byItrial and error. I V p The foregoing will explain the principles and advantages of the preferred embodiment of the invention. By providing a matrix whichis substantially, invariant in cross-section as temperaturechanges, a simple diaphragm seal of fixed shape can be used without any considerable leakage past the diaphragm.

By way of instructive example, major dimensions of one labyrinth element "embodying the invention may be stated. The corrugated sheet 40 is approximately 8" by 2", overall, including the tabs 41, is made of 0.003" type 321 stainless steel with corrugations of 0.04 pitch approximately 0.0125 deep. Bar 43 is stainless steel, type nular body defining passages .for the flow of fluids to establish a temperature gradient between the opposite sides of said body, said annular body including sealing plates spaced around the matrix axis and lying in planes extending along the latter, each of said sealing plates comprising a sheet with opposite marginal portions extending from the annular body for sealing purposes and having a low effective moment of. inertia in a plane normal to said opposite sides and transverse to the sheet, two parallel and spaced bars of material thicker than that of the sheet and each being fixed to the latter a predetermined distance from the. matrix axis, the aggregate of said bars having a high effective moment of inertia in the above-recited plane transverse to the sheet, and thematerial of one of one of said bars lying toward one side of said body having a coefficient of thermal expansion lower than that of the other bar which lies toward the other side of said body. V

2. A rotary regenerator matrix comprisingan annular body having an axis and opposite sides, said body defining passages for the flow 'of fluids to effect a temperature gradientfrom one of said sides to the other and including sealing plates extending from one said side to the other substantially parallel to the direction of fluid flow, said body also including porous material interposed between each of said sealing plates and the adjacent sealing plates, each of the sealing plates comprising a sheet having opposite marginal portions projecting slightly from the said porous material at said sides, and two spaced bars fixed rigidly to the sheet and extending generallyparallel to the said sides, the sheet having a low eifective moment of inertia in a plane normalto said sides and transverse to the sheet and the aggregate of said bars having a high etiective moment of inertia in the same plane compared to the sheet so that the elfective moment of inertia of the sealing plate in the said plane is due primarily to the bars and due only to a minor extent to the sheet, the

materials of said bars having different .coefiicients of thermal expansion to counteract the tendency of the sheet to bow in response to heat elfecting the said temperature gradient, the bar lying toward the hotter side of the matrix having a lower coetficient than the other bar.

3. A matrix as recited in claim. 2 inwhich the said coeflicients are so selected that the thermal expansions of the bars during heat exchange operation are approximately equal.

4. A matrix as recited in claim 2 in which the thermal expansion of the bars during operation serve to compensate for the distortion transmitting effect of said porous material and in maintaining the said marginal portions of said sealingplates along lines elfective for sealing.

5. A matrix as recited in claim 2 in which the bars are thicker than the sheet in the dimension perpendicular to the sheet'and are much narrower than the sheet in the direction parallel to the sheet.

References Cited by the Examiner UNITED STATES PATENTS 3,088,518 V 5/63 Rayburn 9 CHARLESISUKALO, Primary Examiner. 

1. AN ANNULAR REGENERATOR MATRIX COMPRISING AN ANNULAR BODY DEFINING PASSAGES FOR THE FLOW OF FLUIDS TO ESTABLISH A TEMPERATURE GRADIENT BETWEEN THE OPPOSITE SIDES OF SAID BODY, SAID ANNULAR BODY INCLUDING SEALING PLATES SPACED AROUND THE MATRIX AND LYING IN PLANES EXTENDING ALONG THE LATTER, EACH OF SAID SEALING PLATES COMPRISING A SHEET WITH OPPOSITE MARGINAL PORTIONS EXTENDING FROM THE ANNULAR BODY FOR SEALING PURPOSES AND HAVING A LOW EFFECTIVE MOMENT OF INERTIA IN A PLANE NORMAL TO SAID OPPOSITE SIDES AND TRANSVERSE TO THE SHEET, TWO PARALLEL AND SPACED BARS OF MATERIAL THICKNESS THAN THAT OF THE SHEET AND EACH BEING FIXED TO THE LATTER A PREDETERMINED DISTANCE 